Omineca Region Stocked Lake Assessment Report

Transcription

1 Executive Mackenzie Lake #1 West 2004 Stocking assessments were conducted at Mackenzie Lake #1 West in 2000, 2003 and 2004 to determine the status of the fishery. Mackenzie Lake #1 West is 16.9 ha and is situated 42 km South West of Prince George along the Blackwater Forest Service Road. Mackenzie Lake has good 2wd public access and a Forest Service Recreation Site with a launch suitable for car-top boats. The original management goal for Mackenzie Lake was to maintain an average quality fishery. Following these assessments, this goal was changed to management for an above average fishery with the objective of providing an average fish size of greater than 40 cm. One standard floating gillnet 90 m in length (standard mesh) was set on October 26, 2003 and four sinking gill nets were set on June July 4 and July and 28, The total sampling effort in 2003 was 25.5 hours resulting in a gillnet catch per unit effort (CPUE) of 3.73 fish per net hour. The total sampling effort in 2000 was 27 hours resulting in a gillnet catch per unit effort (CPUE) of 1.56 fish per net hour. A third assessment was completed in 2004 to assess reports of a fishkill at ice-off in The rainbow trout sampled during the assessments are reaching sizes suitable to provide for a average quality angling experience, with of significant proportion of the catch reaching lengths greater than 40 cm. Mean fish size in the net catch was approximately 34 cm in 2003 and 24 cm in Maximum fish size in 2003 was 49 cm for a fish estimated to be 5 years of age. Mackenzie West has demonstrated periodic summer oxygen depletion a meter or two below the surface (Omineca Lakes Files), and based on the 2004 gillnet assessment it is clear that at least a partial winter kill occurred in Growth checks were also observed in scales from samples collected in 2003 and may be linked to low summer oxygen. Adipose fin marked RB were stocked in 2004 and are scheduled for stocking in 2005 to validate ages from future stock assessments. Periodic winter kill events and summer oxygen depletion make interannual comparisons of growth difficult, however the growth rates observed for Mackenzie West suggest that management of this lake with an objective of providing an above average fishery is possible. It is recommended that the next stock assessment on Mackenzie lakes should be completed in 2007; the objective of these follow-up assessment are 1) to evaluate management changes on Mackenzie East and 2) evaluate the connectivity of these two lakes using adipose fin marked fish. If there is substantial movement of fish between the two lakes, consideration should be given harmonizing regulations and stock/ strain types used on both systems. Figure 1. Photo of Mackenzie Lake #1 (West) facing East away from the boat launch. Page 1

2 OMINECA REGION LAKE STOCK ASSESSMENT REPORT LAKE NAME: 0 ALIAS: Mackenzie #1 West BC WBID: 01241LCHL LAKE LOCATION: Nearest center: 42 km SSW Prince Georg Drainage: FRASER UTM: LAKE ATTRIBUTES: Surface Area: 16.9 Ha Elevation: 854 m Littoral Area: 13.3 Ha T.D.S.: 96 ppm Max Depth: 9 m Mean depth: 3.8 m MANAGEMENT OBJECTIVE (mean length in gillnet (cm)): Objective 1 Family Fishery (High CPUE <30 cm) Objective 2 Average Quality (30-40 cm) Objective 3 Above Average (40-50 cm) Objective 4 Trophy ( 20% > 50 cm for RB, 20% > 40 cm for EB) X MANAGEMENT/SURVEY HISTORY : Previous gill net assessment(s): no yes X CSTC 2000 Year(s) Surveyed:,1988, 2000, 2003, 2004 PG Lakes Files 1988 STOCKING DATA: Current Stocking Rate 148 Fish/Ha Stocking Interval Stock Type TUNKWA Species RB mixed Previous Stocking Rate 148 SURVEY METHODS: Method Date (yy.mm.dd) Survey Agency Crew Fish SGN BCCF Grant Carlson, Marcel Macullo Chem. Profile 1984 MOE B Little, MOE, PG Lakes Files Physical Bathymetric 1984 MOE B Little, MOE, PG Lakes Files Temp. Profile 1984 MOE B Little, MOE, PG Lakes Files Netting Specs: Net type: Standard Experimental Net length: 90m (3x30m) Setting: Floating Panel Mesh: Standard SURVEY RESULTS: Catch RB EB RSC LKC LSU CSU NSC CAS BT LT Survey Year Effort Hours RB CPUE: RB/Net Hour EB CPUE: EB/Net Hour Next Assessment 2007 # of Sets: Page 2

3 SURVEY CONCLUSIONS: Objectives Achieved Objective Yes No Reason 1. Family 2. Average 3. Above Average X 22 percent of sample was larger than 40 cm 4. Trophy x no fish were larger than 50 cm RECOMMENDATIONS: Assessment: Re-assess in monitor changes in length frequency of fish greater than 40 cm and greater than 50 cm. Assess both Mackenzie Lake at same time to- look for presence of marked fish in Mackenzie East to assess connectivity between lakes. Management: Consider future regulation changes for Mackenzie West so that they are concordant with Mackenzie East. Growth rates from Mackenzie West appear to be high, and this lake may have more potential than Mackenzie East for quality fishery. Effort in 2001, as measured by SLIM boat counts indicated that Mack. West attracted less fishing effort than East. Comments: Uncertainties: 1) There were reports of a winter kill in spring 2004, associated with multiple reports of poor fishing success. The author checked the lake a few days after ice-off and observed one decomposing RB near the boat launch. A limited gill net assessment was conducted in fall 2004 to investigate a reported winter kill at ice-off in spring The growth trajectory (rapid) of RB captured in 2004 and the lack of fish under 200 mm suggests that there was a partial winter kill and not a complete kill. 2) Regulations were changed in 2004 in Mackenzie #2 East to increases opportunities for trophy fish. New regulations- Single barbless hook, bait-ban. 3 fish under 40 cm may be retained. Winter closure. November 1- April 30. 1) Mackenzie West has demonstrated periodic summer oxygen depletion a meter or two below the surface (Omineca Lakes Files). Growth checks were observed in scales from samples collected in 2003 and may be linked to low summer oxygen. Adipose marked RB were stocked in 2004 and are scheduled for stocking in 2005 to validate ages from future stock assessments. 2) Periodic winter kill events and summer oxygen depletion make interannual comparisons of growth difficult. Recent Brood Request Comments: Assessed in fall '03. Multiple growth checks (may have low winter O2). Change stock to BLACKWATER- Lake Chubb Present. History of Angling Regulations Regional regulations Apply. No Special Restrictions Reported by: Date: Cory Williamson Jun-05 Page 3

4 Table 1. Rainbow trout physical attributes for all sample years by age: Sample Paste 'Special' Sample Table in this cell Year Age Size Mean Min Max StdDev Mean Min Max StdDev Mean Min Max StdDev Var Table 2. Catch summary for all sample years. Paste 'Special' Table in this cell Length (mm) Weight (g) Condition (k) Sample Year Sample Size Mean Min Max StdDev Mean Min Max StdDev Mean Min Max StdDev Var Table 3. Proportion of Catch (by survey year) Survey Year Less than 250 mm 17.9 % 50.0 % 23.3 % 6.3 % Between mm 31.6 % 23.8 % 53.3 % 81.3 % Between mm 60.0 % 47.6 % 56.7 % 93.8 % Greater than 400 mm 23.2 % 4.8 % 23.3 % 0.0 % Greater than 500 mm 0.0 % 0.0 % 3.3 % 0.0 % Page 4

5 Weight (g) y = 1E-05x R 2 = y = 8E-06x R 2 = y = 2E-06x R 2 = y = 1E-05x R 2 = Length (mm) Figure 2. Length weight power relationship. Percentage of Sample Age 1+ Age2+ Age 3+ Age Length Class (mm) Figure 3. Length frequency distribution. Age brackets apply to the 2004 data only. Dash line indicates approximate 3+ age class Figure 4. Bathymetric map of Mackenzie #1 (West). Net set locations where available are listed NETs 1 & NET NET 1 Temp/ Oxygen Profile NET NETs 1 & 4 Page 5

6 Table 4. Stocking History for Mackenzie Lake #1 (West) to Release Date Species Name Fish Count Stock Mark Average Size (gm) Life Cycle Stage 8-Jun-05 RB 2500 TUNKWA YEARLING 25-May-04 RB 2500 PENNASK PREM Adipose 7.16 YEARLING 4-Jun-03 RB 2500 BADGER TUNKWA 7.91 YEARLING 19-Jun-02 RB 2500 BADGER TUNKWA YEARLING 30-May-01 RB 2500 NRT DRAGON 9.52 YEARLING 30-May-00 RB 2500 NRT PREMIER 9.9 YEARLING 2-Jun-99 RB 2500 BADGER TUNKWA 13.9 YEARLING 29-May-98 RB 2500 BADGER TUNKWA 7.75 YEARLING 12-Jun-97 RB 2500 BADGER TUNKWA 7.35 YEARLING 4-Jun-96 RB 2500 BEAVER 4.63 YEARLING 8-Jun-95 RB 2500 TUNKWA GE 9.43 YEARLING 11-Jun-94 RB 2500 TUNKWA 7.46 YEARLING 27-May-93 RB 2500 TUNKWA 3.37 YEARLING 30-May-92 RB 2500 NRT PREMIER 6.58 YEARLING 28-May-91 RB 2500 NRT PREMIER 6.32 YEARLING 28-May-90 RB 2500 BADGER 19.8 YEARLING 18-May-89 RB 5000 TUNKWA 7.3 YEARLING 1-Jun-87 RB 2500 NRT PREMIER 2.4 UNKNOWN 1-May-86 RB 2500 NRT PREMIER 4.5 UNKNOWN 1-Jun-85 RB 2500 NRT PREMIER 3.5 UNKNOWN 1-May-84 RB 2500 NRT PREMIER 6.5 UNKNOWN 1-May-82 RB 5000 BADGER DR 5.5 UNKNOWN 1-May-81 RB 5000 NRT PREMIER 6.4 UNKNOWN 1-Jun-80 RB 5000 NRT PREMIER 5 UNKNOWN 1-Jan-79 RB NRT PREMIER 3.4 UNKNOWN 1-May-81 RB 5000 NRT PREMIER 6.4 UNKNOWN 1-Jun-80 RB 5000 NRT PREMIER 5 UNKNOWN 1-Jan-79 RB NRT PREMIER 3.4 UNKNOWN Page 6

7 Table 5. Dissolved Oxygen/ Temperature Profile 28-Jun Jul-00 Station UTM n/a Depth (m) DO Temp. 0 C Depth (m) DO mg/l DO %sat Temp. 0 C ph Cond (25 o C) Table 6. Stock Assessment Data for 2000 (see lake files for additional survey data). Lake Sample# Site Number Species Origin Age Length Weight Condition Scale Age Structure Cond. Clip Sex Maturity Mackenzie RB s 1 f M Mackenzie RB s 1 f ST Mackenzie RB s 3 m ST Mackenzie RB s 1 f M Mackenzie RB s 1 m ST Mackenzie RB s 1 f im Mackenzie RB s 1 f im Mackenzie RB s 1 f im Mackenzie RB s 1 im Mackenzie RB s 1 im Mackenzie RB s 1 im Mackenzie RB s 1 im Mackenzie RB s 1 m ST Mackenzie RB s 1 im Mackenzie RB s 1 im Mackenzie RB s 1 im Mackenzie RB s 1 im Mackenzie RB s 1 im Mackenzie RB s 1 im Mackenzie RB s 1 im Mackenzie RB s 1 im Mackenzie RB s 1 im Mackenzie RB s 1 im Mackenzie RB s 1 im Mackenzie RB s 1 im Mackenzie RB s 1 im Mackenzie RB s 1 im Mackenzie RB s 1 im Mackenzie RB s 2 f M Mackenzie RB s 1 m ST Mackenzie RB s 1 m ST Mackenzie RB s 2 f MT Mackenzie RB s 2 m ST Mackenzie RB s 1 f MT Mackenzie RB s 2 f ST Mackenzie RB s 2 f MT Mackenzie RB s 2 m ST Mackenzie RB s 2 f ST Mackenzie RB s 1 m ST Mackenzie RB s 1 m ST Mackenzie RB s 2 f ST Mackenzie RB s 2 f ST Page 7

8 Table 7. Stock Assessment Data for 2003 (see lake files for additional survey data). Lake Sample# Site Number Species Origin Age Length Weight Condition Scale Age Structure Cond. Clip Sex Maturity Mackenzie Rb S 1 No M Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 2 No F Mt Mackenzie Rb n/a S 9 No M Mt Mackenzie Rb S 2 No M Mt Mackenzie Rb S 1 No M Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No M Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No M Mt Mackenzie Rb S 1 No M IM Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No M Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 2 No F Mt Mackenzie Rb S 1 No Unk IM Mackenzie Rb S 1 No M Mt Mackenzie Rb S 1 No M Mt Mackenzie Rb S 2 No F Mt Mackenzie Rb S 1 No Unk IM Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No M Mt Mackenzie Rb S 1 No M Mt Mackenzie Rb S 1 No M Mt Mackenzie Rb S 1 No M Mt Mackenzie Rb S 1 No M Mt Mackenzie Rb S 2 No M Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 9 No M Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No M Mt Mackenzie Rb S 1 No M Mt Mackenzie Rb S 1 No M Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 2 No F Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No M Mt Mackenzie Rb S 1 No M Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 8 No M Mt Mackenzie Rb S 9 No M Mt Mackenzie Rb S 1 No M Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 2 No M Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb E-05 S 1 No M Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 3 No M Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No M Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No Unk IM Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb #DIV/0! S 1 No Unk Mt Mackenzie Rb S 1 No M Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No M Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No M Mt Mackenzie Rb S 1 No M Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No M Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 3 No F Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No M Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No M Mt Mackenzie Rb S 1 No M Mt Mackenzie Rb S 1 No F Mt Mackenzie Rb S 1 No M Mt Mackenzie Rb S 3 No M Mt Page 8

9 Table 8. Stock Assessment Data for 2004 (see lake files for additional survey data). Lake Sample# Site Number Species Origin Age Length Weight Condition Scale Age Structure Cond. Clip Sex Maturity Ageing Com Mackenzie rb un Mackenzie rb un Mackenzie rb un Mackenzie rb un Mackenzie rb un Mackenzie rb un Mackenzie rb un Mackenzie rb un Mackenzie rb un Mackenzie rb un Mackenzie rb un Mackenzie rb un Mackenzie rb un Mackenzie rb un Mackenzie rb un Mackenzie rb un Page 9